The annulate lamellae of salamander oocytes: Morphological and functional aspects

Summary The present study reports observations on the distribution, morphology and functional significance of annulate lamellae in the developing salamander oocyte. This organelle was found in the cytoplasm, both as individual elements and as a cluster made up of from two to approximately five lamellae organized into closely aligned stacks. Adjacent stacks of lamellae were found to be randomly oriented. Annulate lamellae are essentially identical in structure with the nuclear envelope. The terminations of lamellae were very frequently found to be expanded into sac-like structures. The outer surface of each sac is usually lined with ribosomes. The paired membranes in some of the lamellae exhibited dilations for varying distances from their terminal sacs. These dilated segments of the lamellae were also lined with ribosomes. The annulate lamellae were interpreted as being intermediate stages in the formation of rough-surfaced cisternae and would, therefore, represent structural precursors of a form of endoplasmic reticulum. This organelle may therefore represent a transient morphological response to a need for especially high concentrations of proteins.

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Zusammenfassung Die vorliegende Arbeit berichtet Beobachtungen über Verteilung, Morphologie und funktioneile Bedeutung von Annulate lamellae in der sich entwickelnden Oocyte von Salamandern. Diese Organellen wurden im Zytoplasma gefunden, sowohl als individuelle Elemente, als auch in Gruppen, die aus etwa zwei bis fünf nahe beieinanderliegenden Stapeln organisierten Lamellen bestehen. Aneinandergrenzende Stapel von Lamellen sind zufÄllig orientiert. Annulate lamellae sind in ihrer Feinstruktur im Wesentlichen mit der Kernmembran identisch. Die Enden von Lamellen waren sehr oft als sackförmige Strukturen ausgebildet. Die Äu\ere OberflÄche eines Sackes ist im allgemeinen mit Ribosomen besetzt. In einigen der Lamellen zeigten die gepaarten Membranen Ausweitungen über variierende Distanzen von ihren TerminalsÄcken. Diese ausgeweiteten Teilstücke der Lamellen waren ebenfalls mit Ribosomen besetzt. Die Beobachtungen werden dahin interpretiert, da\ die Annulate lamellae intermediÄre Stadien in der Bildung von granulÄren Zisternen sind und deshalb strukturelle VorlÄufer einer Form des endoplasmatischen Retikulums darstellen. Die Organelle mag deshalb eine vorübergehende morphologische Reaktion auf einen Bedarf von besonders hoher Proteinkonzentration darstellen.

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This investigation was supported by a Public Health Service research career program award (5-K3-HD-5356-07) from the National Institute of Child Health and Human Development.     

Fitting Circles and Spheres to Coordinate Measuring Machine Data

This work addresses the problem of enclosing given data points between two concentric circles (spheres) of minimum distance whose associated annulus measures the out-of-roundness (OOR) tolerance. The problem arises in analyzing coordinate measuring machine (CMM) data taken against circular (spherical) features of manufactured parts. It also can be interpreted as the “geometric” Chebychev problem of fitting a circle (sphere) to data so as to minimize the maximum distance deviation. A related formulation, the “algebraic” Chebychev formula, determines the equation of a circle (sphere) to minimize the maximum violation of the equation by the data points. In this paper, we describe a linear-programming approach for the algebraic Chebychev formula that determines reference circles (spheres) and related annuluses whose widths are very close to the widths of the true geometric Chebychev annuluses. We also compare the algebraic Chebychev formula against the popular algebraic least-squares solutions for various data sets. In most of these examples, the algebraic and geometric Chebychev solutions coincide, which appears to be the case for most real applications. Such solutions yield concentric circles whose separation is less than that of the corresponding least-squares solution. It is suggested that the linear-programming approach be considered as an alternate solution method for determining OOR annuluses for CMM data sets.     

5,7-Dihydroxy-3,6,8-trimethoxyflavone from the flowers of Gnaphalium elegans

5,7-Dihydroxy-3,6,8-trimethoxyflavone was isolated from the flowers of Gnaphalium elegans. The structure elucidation is based mainly on proton resonance studies using Eu(fod)₃ shift reagent.     

The enzymatic synthesis of heterogeneous dihalide derivatives: a unique biocatalytic discovery

Using purified enzymes, the first transformations of unhalogenated organic substrates to heterogeneous dihalogenated products are reported, including the first enzyme-associated synthesis of a carbon—fluorine bond.     

Chaperone-fusion expression plasmid vectors for improved solubility of recombinant proteins in Escherichia coli

The enteric bacterium Escherichia coli is the most extensively used prokaryotic organism for production of proteins of therapeutic or commercial interest. However, it is common that heterologous over-expressed recombinant proteins fail to properly fold resulting in formation of insoluble aggregates known as inclusion bodies. Complex systems have been developed that employ simultaneous over-expression of chaperone proteins to aid proper folding and solubility during bacterial expression. Here we describe a simple method whereby a protein of interest, when fused in frame to the E. coli chaperones DnaK or GroEL, is readily expressed in large amounts in a soluble form. This system was tested using expression of the mouse prion protein PrP, which is normally insoluble in bacteria. We show that while in trans over-expression of the chaperone DnaK failed to alter partitioning of PrP from the insoluble inclusion body fraction to the soluble cytosol, expression of a DnaK–PrP fusion protein yielded large amounts of soluble protein. Similar results were achieved with a fragment of insoluble Varicella Zoster virus protein ORF21p. In theory this approach could be applied to any protein that partitions with inclusion bodies to render it soluble for production in E. coli.